Over at American Scientist, Wendy M. Williams and Stephen J. Ceci describe the extreme gender imbalance in scientific careers in America, where women hold, on average, only 4.4 to 12.4 percent of full professorships in scientific fields. This imbalance is not nearly as marked in Europe and Asia. What's keeping American women out of science? Williams and Ceci say it's just one thing: child rearing. They write:

The usual explanations for the shortage of women focus squarely on sex discrimination at various life stages. As a result of such discrimination, the argument goes, girls and women drop out of math-based endeavors or change their focus. Some scholars have argued for the effects of early socialization practices that lead girls along a path that downplays math-pink versus blue attire for babies, Barbie dolls proclaiming "Math class is tough," middle-school math teachers calling on boys more than girls, high-school girls urged to be cheerleaders or writers instead of scientists. Others invoke gender stereotypes-sets of shared cultural expectations that suggest, for instance, that females are not gifted in math or that the responsibility for raising children belongs primarily or solely to women. Still others look further down the pipeline, at disenfranchisement of women once they enter academic-science careers, focusing on claims of "chilly climate"; unequal pay and promotion; devaluing of women's work styles and biased assessment of their efforts; and old-boys' clubs that isolate women. Researchers have also studied the role of sex differences at the extreme right tail of the math distribution-more boys than girls demonstrate extremely high levels of math ability on standardized tests such as the SAT. Still others suggest that women simply prefer to use their math and science skills to be veterinarians and biologists, for example, rather than engineers and computer scientists, and that the difference in the numbers can be explained by this freely determined preference.

We argue for the importance of another factor in women's underrepresentation: the choice to become a mother. To place the role of this choice in context, we consider its impact on women's careers relative to the impacts of other variables that may reduce women's participation in the sciences. Our own findings as well as research by others show that the effect of children on women's academic careers is so remarkable that it eclipses other factors in contributing to women's underrepresentation in academic science.

It's a fascinating argument, which suggests that scientific institutions are structured to reward people who don't engage in very much childcare.